Telephony



Dec. 9, 1941. w. SIX 2,265,203

TELEPHONY Filed April 26, 1959 BIA/EM ro/r 14 6212c Patented Dec. 9,1941 UNITED STATES PATENT OFFICE 2,265,203 rausrnomr Willem Six,Eindhoven, Netherlands, assignor, by mesne assignments, to HartfordNational Bank and Trust Company, Hartford, Conn., as

My invention relates to telephony systems and more particularly tosignal receivers for such systems. I

My invention is particularly concerned with signal receivers forreceiving signalling currents which are transmitted directly or bycarrier waves over a conductor which may also be used for speechtransmission, and which currents have a frequency located in or adjacentto the frequency range of the speech currents or the speech sideband.

As is well known, signal receivers of the above type must be such thatthe signal circuit cannot be erroneously energized by speech currents ofa frequency which is the same as or close to the frequency of the signalcurrents.

The main object of my invention is to provide a signal receiver withwhich the signal circu't can be energized only by the signal currents.

A further object is to provide a signal receiver which is simple inconstruction and reliable in operation.

Further objects and advantages will appear as the descriptionprogresses.

In accordance with the invention I control the signal circuit by tworelays or relay combinations of which one sets the signal circuit intooperation with a time-lag and the other sets the signal circuit intooperation without a time-lag, and make the time-lag of such durationthat the signal circuit will not be established by current pulses causedby speech currents of a frequency close to or equal to the signalcurrent frequency.

In order that the invention may be clearly understood and readilycarried into effect, I shall describe the same in more detail withreference to the accompanying drawing in which Figure I is a schematicdiagram of a signal receiver according to one embodiment of theinvention, and

Figure II is a schematic diagram of a signal receiver according toanother embodiment of the invention.

The signal receiver shown in Figure I comprises a transformer 3 having aPrimary winding 9 whose terminals I and 2 are adapted to be connected toa telephony transmission line (not shown) transmitting bothlow-frequency signal currents and speech currents. If the signalcurrents are transmitted by carrier wave over a conductor, the terminalsI and 2 would be connected to the output circuit of a demodulator whichdemodulates both the modulated signal currents and the speech currentsreceived. Thus, in any case both low-frequency signal currents andspeech currents are supplied to terminals I and 2.

Transformer 3 has a secondary winding ii tuned to the signal frequencyby a condenser l, and having one end connected through a conductor H tothe grid of a triode 5, which is connected as an anode rectifier, andhaving its other end connected through a biasing battery I! to thecathode of tube 5.

The receiver also comprises two relays l3 and II having normally-openarmatures l5 and I6 respectively connected in series in a signal circuit6. Armature i5 acts instantaneously, whereas armature i6 acts with apredetermined time delay both in opening and closing. As time-delayrelays of this type are well known in the art further description of thesame is believed. unnecessary.

The coils of relays i3 and H are connected in parallel in the platecircuit of tube 5 and for this purpose one end of each coil is connectedthrough a conductor I! to the plate of tube 5, and the other ends of thecoils are connected together and through a battery I and a conductor l8to the cathode of tube 5, a condenser 8 connected across the plate andcathode of tube 5 serve to smooth the rectified plate current.

In operation of the receiver, the signal currents received at terminalsI and 2 produce a rectified voltage across the coils of both relays l3and H. Relay I3 is energized and armature i5 closes its contactpractically instantaneously but relay I 4 becomes energized and armatureit closes its contact only after a predetermined time interval. Thus,the signal circuit 8 is established only at a predetermined time aftervoltage is applied to the coils of relays i3 and I.

When the speech currents received containcomponents whose frequenciesare located adjacent the signal frequency and produce a voltage at thegrid of tube 5 for a short time, the rectified voltage applied acrossthe coils of relays I 3 and H causes armature l5 to close immediatelywhereas armature l6 remains open for a short time period. As thosecomponents of the speech currents whose frequencies are located adjacentthe signal frequency occur for only a short time interval, armature Itwill not be closed by such currents, provided, of course, the time-lagin relay I4 is made longer than the duration of such currents. Inpractice, the relay it may have a timelag of about second. When signalcurrents consisting of successive impulses are received the relay l3opens and closes its armature ii in the rhythm of these impulses, thearmature II of the relay It remains, however, closed due to the timelagof about lit-V10 second which is longer than the duration of eachinterval between two successive signal impulses. By the closing andopening of the armature I! of relay It the signal impulses aretransmitted in the signal circuit 8.

The receiver shown in Figur 2 is similar in many respects to that ofFigure l and the same reference numerals are used to designate the sameparts. However, in Figure 2 the relay ll of Figure 1, which relay isenergized and de-energized with a time-lag, is replaced by two relays 2.and 22 having normally-closed armatures 2| and 23 respectively, both ofthe latter relays being energized quickly but de-energized with atime-lag. The coil of relay 20 is connected in parallel with the coil ofrelay l3, whereas armature' 2! controls a circuit comprising the coil ofrelay 22 and a battery 24. Armature 23 is connected in serieswith-armature IS in the signal circuit 8.

When signal currents are received at terminals I and 2, rectifiedvoltage is applied across the coils of relays l5 and 20 with the resultthat the armature I5 closes immediately and armature 2| immediatelyopens and causes deenergization of relay 2!. After a suitable timeinterval armature 23 closes to thereby establish the signal circuit 6.

It the signal currents are constituted by a number of periodical pulses,armature l5 of relay l3 will open and close periodically so that thesepulses are transmitted in the signal circuit 6. Although theenergization of relay 20 is periodically interrupted by these pulses,this relay is deenergized with a time-lag, and thus the armature 2| willremain open, relay 22 will remain deenergized and armature 23 willremain closed.

When receiving speech-current components of short duration armature 2|is also opened, but due to the fact thatrelay 22 is de-energized with atime-lag, armature 23 is prevented from closin and thus the signalcircuit 6 will not be erroneously established by these speech currents.

The signal receiver as shown in Fig. 2 has the advantage over that shownin Fig. 1, that the relay combination 20 and 22 contains relays whichare only de-energized with a time-lag i. e. have v a time delay in onlyone direction. Such relays are more readily constructed than a relaysuch as the relay Id of Figure 1 which has to be energized as well asde-energized with a time-lag.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and discussed or to the use of timerelays of any particular type, because obvious modifications will occurto a person skilled in the art.

What I claim is: v

l. In a telephony system in which signal currents of a frequency atleast close to the frequency range of the speech-currents or the speechside-band are transmitted over a conductor adapted to serve also forspeech transmission, a local signal circuit, a signal receivercontrolling said local signal circuit and comprising electroresponsivemeans including a contact connected in said circuit and adapted to closeand open without time delays, second electro-responsive means includinga contact connected in said circuit and adapted to close and open withpredeterminedtime delays, and means to simultaneously energize both saidmeans with a voltage produced by the signal currents and speech currentsoi similar frequency.

2., In a telephony system in which signal currents of a frequency atleast close to the frequency range of the speech-currents or the speechside-band are transmitted over a conductor adapted to serve also forspeech transmission, a local signal circuit, a signal receivercontrolling said local signal circuit and comprising an electro-magneticrelay having a contact connected in said circuit and adapted to closeand open without a time delay, a second electromagnetic relay having acontact connected in said circuit and adapted to close and open withpredetermined time delays, and means to simultaneously energize bothrelays with voltage pulses produced by the signal currents and speechcurrents of similar frequency,

3. In a telephony system in which signal currents of a frequency atleast close to the frequency range of the speech-currents or the speechside-band are transmitted over a conductor adapted to serve alsofor-speech transmission, a local signal circuit, a signal receivercontrolling said local signal circuit and comprising an electrical relayhaving a contact connected in said circuit and adapted to close and openwithout a time delay, a second electrical relay having a normally-closedcontact adapted to open with a time delay, a circuit including saidlatter contact and a voltage supply, a third electrical relay having acoil in said latter circuit and a normallyopen contact in said signalcircuit and adapted to open with a time delay, and means tosimultaneously energize the first two relays with voltage pulsesproduced by the signal currents and speech currents of similarfrequency.

4. In a telephony system in which signal currents of a frequency atleast close to the frequency range of the speech-currents or the speechside-band are transmitted over a conductor adapted .to serve also forspeech transmission, a local signal circuit, a signal receivercontrolling said local signal circuit and comprising an electrical relayhaving a normally-open contact connected in said circuit and adapted toclose and open without a time delay, a second electrical relay having anormally-open contact connected in said circuit and adapted to bothclose and open with predetermined time delays, and means tosimultaneously energize both said relays with a voltage produced by thesignal currents and by speech currents of similar frequency.

WILLEM SIX.

